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<div class="os1">7.4 串行化数据流QDataStream</div>
<br>
上节 QTextStream 是针对文本流的处理，QTextStream 中都是人类直接可读的文本形式，但是 QTextStream 有它的局限性，对于
Qt 自己的类对象，QTextStream 仅支持字符相关的 QChar、QString、QByteArray，Qt 还有很多其他类，比如矩形
QRect、像素图 QPixmap、点 QPoint、颜色 QColor 等等，这些都没有规定的字符串形式。<br>
实际程序中会大量用到人类不可读的二进制数据，这些二进制数据的封装和存储、传输，就需要用串行化数据流 QDataStream 实现，对于 Qt
知道的所有数据类型，包括 C++ 基本类型变量和 Qt 自己类对象，都可以使用 QDataStream
自动打包成整体的数据块（将各种类型变量和对象按顺序打包就是串行化，按顺序解包就是反串行化），可以用于网络传输和本地文件读写。<br>
本节先介绍 QDataStream 类的内容，然后编写一个使用 QDataStream 自定义文件格式做输入输出的例子。对于网络数据的封包解包示范，等到
网络传输章节再介绍，目前可以回顾 3.4.3 节的串行化打包例子。本节最后介绍第二个例子，自定义一个结构体，然后让我们自己的结构体支持串行化输入输出。<br>
<br>
<div class="os2">7.4.1 QDataStream 类</div>
<br>
QDataStream 可以支持对输入输出设备的串行化，也可以支持对 QByteArray 字节数组的输入输出，它的构造函数如下：<br>
<div class="code"> QDataStream(QIODevice * d)</div>
<div class="code"> QDataStream(QByteArray * a, QIODevice::OpenMode mode) </div>
<div class="code"> QDataStream(const QByteArray & a)</div>
第一个构造函数是用于支持 I/O 设备，需要在传递指针给 QDataStream 之前把设备打开，比如提前打开文件，然后把文件对象指针传给
QDataStream。<br>
第二个构造函数一般用于支持 QByteArray 的读写，传递字节数组的指针，并且需要指定读写模式，一般是用 QIODevice::ReadWrite。<br>
第三个构造函数参数为字节数组的常量引用，字节数组是只读的，仅作为输入来使用。<br>
除了构造函数，还有如下设置函数改变当前 QDataStream 对象的设备：<br>
<div class="code">void QDataStream::setDevice(QIODevice * d)</div>
<br>
QDataStream 使用的是 Qt 自定义的数据打包格式，这种数据打包格式与操作系统、硬件是 100% 无关的，用 QDataStream
打包的数据包，无论是在 Intel + Windows 、还是 Sun SPARC + Solaris、ARM + Andorid
等等，都可以通用，不用管 CPU 字节序。<br>
对于所有 C++ 基本类型变量，QDataStream 提供了一系列的 << 和 >> 运算符重载函数，比如整型的：<br>
<div class="code">QDataStream & QDataStream::operator<<(qint32 i)</div>
<div class="code">QDataStream & QDataStream::operator>>(qint32
& i)</div>
这些都是 QDataStream 的成员函数，还有其他的比如输入输出 bool、qint64、float、double 等等。<br>
<br>
对于 C++ 整型数的读写，需要特别注意 long 类型，在 32 位系统，long 类型是 32 bit 长度，而在 64 位系统，long 是 64
bit 长度，因为这种不确定性，所以整型变量都应该转为 Qt
预定义的类型：qint8、quint8、qint16、quint16、qint32、quint32、qint64、quint64，这样能保证变量的长度是类型名字
里指定的位数，无论在什么操作系统都不会出错。<br>
<br>
对于所有 Qt 数据封装类的对象，在 QDataStream 类里面查不到对应的运算符重载函数，不是没有，而是太多。在 Qt 帮助文档 <span style="font-weight: bold;">Serializing
Qt Data Types </span>页面可以看到所有可以串行化的类型，Qt 自己类对象的串行化，是通过相关的非成员函数（Related
Non-Members），这些非成员函数可以在各个数据封装类自己的文档页面找到，比如 QColor 类的非成员函数：<br>
<div class="code">QDataStream & operator<<(QDataStream &
stream, const QColor & color)</div>
<div class="code">QDataStream & operator>>(QDataStream &
stream, QColor & color)</div>
<br>
对于 QDataStream 流的输入，可以判断当前位置是否到达设备的末尾：<br>
<div class="code">bool QDataStream::atEnd() const</div>
但是 QDataStream 没有 seek() 函数移动游标，也没有游标获取函数 pos() ，这与文本流 QTextStream、文件类 QFile
有很大的区别。在 QDataStream 流里看不到游标，因为它不是按字节或字符读写的，它用 Qt 自家的打包格式（或叫编码方式），只能按变量或类对象顺
序读写，不能随机读写。<br>
串行化，就如它的名字一样，一条道走到黑，输入输出的顺序固定好之后，就不能进行随机位置读写，只能从头按顺序读或从头按顺序写。<br>
<br>
除了 << 和 >> 运算符重载函数，QDataStream 提供了另外几个读写函数，可以用于读写自定义的数据块，首先是一对
writeBytes() 和 readBytes() 函数：<br>
<div class="code">QDataStream & QDataStream::writeBytes(const char * s,
uint len) //变量 len 也会写入数据流</div>
<div class="code">QDataStream & QDataStream::readBytes(char *& s,
uint & l) // l 数值是从数据流里读出来的，就是上面的 len</div>
对于字节写入函数，参数里的 s 是要输出的字节缓冲区，len 是写入数据的长度，这里 s 里面针对纯字节数据，不管里面有没有 '\0' ，都写入
数据流。<br>
对于字节读取函数，s 是指针变量的引用，l 是读取的字节数，s 指针不需要程序员分配空间，由 readBytes() 函数自己 new []
一段缓冲区，然后把缓冲区指针赋值给 s；参数 l 是函数的返回变量，是真实读取到的字节数。函数返回之后 s 指针变量指向的缓冲区需程序员手动
delete [] 。<br>
writeBytes() 函数在做串行化时，会先写 quint32 类型的数据长度，然后写入真实的缓冲区数据到数据流。readBytes()
也是先读取字节数组长度，该函数自己 new [] 一片空间，把后面的真实数据读到缓冲区。<br>
<br>
writeBytes() 和 readBytes() 函数与字符串 读写运算符重载函数有类似的地方：<br>
<div class="code">QDataStream & QDataStream::operator<<(const
char * s) </div>
<div class="code">QDataStream & QDataStream::operator>>(char
*& s)</div>
在做串行化时，都是先写一个 quint32 类型的长度到数据流，然后写真实数据，读的时候就是先读长度，然后根据长度 new []
缓冲区，把数据读到缓冲区。这两对函数的区别就是 writeBytes() 和 readBytes() 针对字节数组，不管是不是 '\0'，都当作普通字
节读写；<< 和 >> 读写字符串时遇到 '\0' 就截止了，并且 '\0' 不会写入到数据流。<br>
<br>
QDataStream 还提供了更裸的读写函数，下面这对读写函数是不把字节数组长度变量写入到数据流的，仅仅写入原始的缓冲区数据：<br>
<div class="code">int QDataStream::writeRawData(const char * s, int len)</div>
<div class="code">int QDataStream::readRawData(char * s, int len)</div>
这对函数与之前一对 writeBytes() 和 readBytes()
函数区别有两点：第一，不写数据长度变量到数据流，只读写最原始的数据块；第二，readRawData()
自己不会分配缓冲区，必须由程序员提前分配缓冲区给 s，然后传递给 readRawData() 函数。<br>
<br>
QDataStream 与 QTextStream
也有类似的地方，就是流的状态，如果数据流的输入顺序与输出顺序不匹配，那么会出现状态错误，获取流的状态函数为：<br>
<div class="code">Status QDataStream::status() const</div>
状态枚举类型也有四个：<br>
<br>
<table class="tabel">
<tbody>
<tr class="d1">
<td style="width: 200px;" align="center"><b>Status 枚举常量</b></td>
<td style="width: 200px;" align="center"><b>数值</b></td>
<td align="center"><b> 描述</b></td>
</tr>
<tr>
<td>QDataStream::Ok</td>
<td> 0 </td>
<td> 正常操作状态，没出错。 </td>
</tr>
<tr class="d1">
<td>QDataStream::ReadPastEnd</td>
<td> 1 </td>
<td> 底层设备已到达末尾，比如文件末尾，无数据可读了。 </td>
</tr>
<tr>
<td>QDataStream::ReadCorruptData</td>
<td> 2 </td>
<td> 读入了腐化数据，典型的就是输入流读取顺序与输出流顺序不一样。</td>
</tr>
<tr class="d1">
<td>QDataStream::WriteFailed</td>
<td> 3 </td>
<td> 无法向底层设备写入数据，比如文件是只读的。 </td>
</tr>
</tbody>
</table>
<br>
在 QDataStream 数据流出现错误状态之后，可以重新设置流的状态：<br>
<div class="code">void QDataStream::setStatus(Status
status) //设置流为参数里执行的状态</div>
<div class="code">void QDataStream::resetStatus()
//重置为原始的 Ok 状态</div>
QDataStream 流的排除处理就比较麻烦了，虽然可以跳过一定的裸字节数：<br>
<div class="code">int QDataStream::skipRawData(int len)</div>
这个函数跳过最原始的裸数据 len 长度的字节，返回值是真实跳过的字节数。这个函数可以与 readRawData()
配合使用，但是在处理流错误时未必有用，因为跳过指定的字节数目之后，流的数据到哪种类型的变量或对象了，难以确定。QDataStream
读取错误时，最好的做法是直接提示出错，后面的不读取，因为串行化数据流默认是不能随机化读写的。<br>
<br>
QDataStream 是使用 Qt 自己独有的串行化数据打包方式，它没有任何的格式操作子，因为输入输出格式全是内置的，但 QDataStream
有自己兼容的 Qt 版本号。随着 Qt 版本的更新，QDataStream 打包数据的方式也会更新，因此 QDataStream
有一大堆兼容的版本号，从最早的 Qt_1_0 到最新的 Qt_5_4，版本号枚举常量的命名规则就是 <span style="font-style: italic;">Qt_
大版本号_小版本号</span> 。<br>
如果负责输出的程序与负责输入的程序，使用的 Qt 版本是一致的，就不需要设置版本号。但是如果输出和输入程序的 Qt 版本不一致，比如输出程序
使用的是 Qt 4.8.* ，输入程序使用的是 Qt 5.4.* ，那么就应该向旧版本兼容，在做读取变量或对象之前，设置版本号：<br>
<div class="code">void QDataStream::setVersion(int v)</div>
要兼容 Qt 4.8.* ，那么就把参数设为 QDataStream::Qt_4_8 。<br>
<br>
随着 Qt 版本号的更新，C++ 基本类型的变量读写规则是固定的，比如 qint32 就是读写 4 个字节，所以 QDataStream 版本号对
C++ 基本类型变量读写其实没影响。QDataStream 版本号影响的是 Qt 自己类对象的读写规则，比如以后如果新增了一个类
QXXXXData，那么只有新版本的 Qt 中 QDataStream 才能读写这个新类 QXXXXData 对象。<br>
<br>
在本小节末尾，我们将 QTextStream 和 QDataStream 简单做一下对比：<br>
<br>
<table class="tabel">
<tbody>
<tr class="d1">
<td style="width: 200px;" align="center"><b>对比项</b></td>
<td style="width: 400px;" align="center"><b>QTextStream</b></td>
<td style="width: 400px;" align="center"><b> QDataStream</b></td>
</tr>
<tr>
<td>用途</td>
<td> 处理文本流，如 QIODevice、FILE句柄、QString、QByteArray，这里的 QByteArray
是作为字符串用途，以 '\0' 为终止符 </td>
<td> 处理二进制数据流，如 QIODevice 、QByteArray ，这里的 QByteArray
作为字节数组，是纯数据，不区分字节数值是否为 0</td>
</tr>
<tr class="d1">
<td><< 和 >> 涵盖的数据类型</td>
<td> C++基本类型和 QChar、QString、QByteArray（字符串）</td>
<td> C++基本类型和 Qt 库中几乎所有用于表示数据的类</td>
</tr>
<tr>
<td>流操作子</td>
<td> 很多格式化操作子，程序员可以控制格式</td>
<td> 没有操作子，打包格式内定，程序员不能控制</td>
</tr>
<tr class="d1">
<td>流的版本号</td>
<td> 没有版本号 </td>
<td> 可以设置从 Qt_1_0 到最新的版本号，不同版本号的串行化打包是有区别的</td>
</tr>
<tr>
<td>流的游标</td>
<td> pos() 获取游标，seek() 移动游标，atEnd() 判断末尾，可以随机化读写</td>
<td> 没有游标，只能用 atEnd() 判断是否到末尾，不能随机化读写，必须按写入时相同的顺序和类型来读取</td>
</tr>
<tr class="d1">
<td>流的工作状态</td>
<td> QTextStream::Status 四种状态</td>
<td> QDataStream::Status 四种状态</td>
</tr>
</tbody>
</table>
<br>
从上面表格可以看到，QTextStream 和 QDataStream 除了都有四种工作状态，其他特性都有差异，二者用途不同，决定差异性很大。<br>
<br>
<div class="os2">7.4.2 自定义文件格式输入输出</div>
<br>
我们在 7.3.5
节例子中表格数据，是采用文本形式存储的，本小节我们自定义一个二进制文件格式，专门存储类似下面的数据表格（下面表格是文本的，只是方便大家看，真实的二进制文件我们例
子结尾用 QtCreator 打开看）：<br>
<div class="code">#QString qint32 double<br>
小明 18 50.5<br>
小萌 19 55.8<br>
小日 17 60.0<br>
小月 16 55.1<br>
小草 18 58.6</div>
因为用二进制数据格式，就不用注释行了，只需要用 QDataStream 写入指定类型数据。<br>
我们这里自定义文件扩展名设置为 .ds ，一般文件都需要一些文件头的结构体信息，我们这里使用 QDataStream 输出文件信息头，我们定义 .ds
文件结构如下：<br>
<center> <img src="images/ch07/ch07-04-01.png" alt="ds file"> </center>
文件首先是一个 qint16 变量，数值为 0x4453，就是字母 'D' 和 'S' 的十六进制数，打头的 0x4453 一般称为魔力数字（magic
number），用于标识文件类型；<br>
然后也是一个 qint16 变量，数值为 0x0100，代表文件格式 1.0 版本；<br>
接着是表格数据的总行数计数 nCount ，之后就是每行的数据（不是文本文件不需要写入换行符，这里的“行”只是方便理解数据的排布）。<br>
文件的写入和读取都用 QDataStream 实现，为了向旧版本的 Qt 兼容，我们这里规定文件格式 1.0 版本对应的
QDataStream 都用 Qt_4_8 的版本号。<br>
<br>
讲完自定义文件格式，下面我们开始编写示例程序，打开 QtCreator，新建一个 Qt Widgets Application
项目，在新建项目的向导里填写：<br>
①项目名称 dsedit，创建路径 D:\QtProjects\ch07，点击下一步；<br>
②套件选择里面选择全部套件，点击下一步；<br>
③基类选择 QWidget，点击下一步；<br>
④项目管理不修改，点击完成。<br>
我们打开 widget.ui 界面文件，先把主界面窗口的尺寸设置为 480*300，然后按照下图拖入控件：<br>
<center> <img src="images/ch07/ch07-04-02.png" alt="ui" width="800"> </center>
界面从左边看是两大行控件：<br>
第一大行，标签控件，文本 "姓名"，单行编辑器，对象名 lineEditName，标签控件，文本 "年龄"，单行编辑器，对象名
lineEditAge，标签控件，文本 "体重"，单行编辑器，对象名 lineEditWeight，最右边是按钮控件，对象名
pushButtonAdd，文本为 "添加行" ，第一大行按照水平布局器排布。<br>
第二大行，左边是一个列表控件，对象名默认为 listWidget；右边是一个垂直布局器，在垂直布局里是三个按钮和垂直弹簧条，首先是 "删除行"
按钮，对象名 pushButtonDel，垂直弹簧条，对象名默认为 verticalSpacer，然后是 "保存DS" 按钮，对象名
pushButtonSaveDS，最下面是 "加载DS" 按钮，对象名为 pushButtonLoadDS，第二大行也是按照水平布局器排布。<br>
窗口的主布局器是垂直布局器，点击界面空白位置，不选中任何控件，再点击上面垂直布局按钮就可以为窗口设置主布局器。这个例子界面与 7.3
节第一个例子相比做了调整，因为本节的 DS 文件原本没有，是我们自创的格式，需要手动在示例程序添加各行数据，然后保存为 *.ds 才会生成 DS 文件。<br>
<br>
界面和布局就是如上所述，现在我们分四次为四个按钮都添加 clicked() 信号对应的槽函数：<br>
<center> <img src="images/ch07/ch07-04-03.png" alt="slot1"> </center>
然后为列表控件 listWidget 添加 currentRowChanged(int) 信号对应的槽函数：<br>
<center> <img src="images/ch07/ch07-04-04.png" alt="slot5"> </center>
添加好槽函数之后，我们保存界面文件，然后关闭界面文件，回到代码编辑模式。<br>
对于头文件 widget.h ，不需要手动添加代码，都是自动生成的，下面仅仅贴出来看看：<br>
<div class="code"><span style=" color:#000080;">#ifndef</span><span style=" color:#c0c0c0;">
</span>WIDGET_H
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#define</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">WIDGET_H</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;"><QWidget></span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">namespace</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Ui</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">class</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Widget</span><span style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">class</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Widget</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">:</span><span style=" color:#c0c0c0;"> </span><span style=" color:#808000;">public</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QWidget</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000080;">Q_OBJECT</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">public</span><span style=" color:#000000;">:</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">explicit</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">Widget</span><span
style=" color:#000000;">(</span><span style=" color:#800080;">QWidget</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">*</span>parent<span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">0</span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">~</span><span style=" font-style:italic; color:#000000;">Widget</span><span
style=" color:#000000;">();</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">private</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#808000;">slots</span><span style=" color:#000000;">:</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonAdd_clicked</span><span
style=" color:#000000;">();</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonDel_clicked</span><span
style=" color:#000000;">();</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonSaveDS_clicked</span><span
style=" color:#000000;">();</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_pushButtonLoadDS_clicked</span><span
style=" color:#000000;">();</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">void</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">on_listWidget_currentRowChanged</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span>currentRow<span
style=" color:#000000;">);</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#808000;">private</span><span style=" color:#000000;">:</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">Ui</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">Widget</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">*</span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">};</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#endif</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">//</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">WIDGET_H</span></pre>
</div>
头文件有五个槽函数，我们需要在 widget.cpp 里面添加功能代码，下面我们打开 widget.cpp ，首先添加头文件包含和构造函数里的代码：<br>
<div class="code"><span style=" color:#000080;">#include</span><span style=" color:#c0c0c0;">
</span><span style=" color:#008000;">"widget.h"</span>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">"ui_widget.h"</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;"><QDebug></span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;"><QMessageBox></span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;"><QFileDialog></span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">//文件对话框</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;"><QFile></span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">//文件类</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;"><QDataStream></span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">//串行化数据流，用于读写</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">.ds</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">文件</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;"><QTextStream></span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">//用于列表控件显示的文本和数据转换</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000080;">#include</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;"><QListWidgetItem>//用于从列表控件的行提取文本</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">Widget</span><span style=" color:#000000;">(</span><span
style=" color:#800080;">QWidget</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">*</span><span style=" color:#000000;">parent</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">:</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QWidget</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">parent</span><span
style=" color:#000000;">),</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">new</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">Ui</span><span style=" color:#000000;">::</span><span style=" color:#800080;">Widget</span><span
style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-></span><span style=" color:#000000;">setupUi</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//设置列表控件只能选中一行，简化删除行的操作</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-></span><span style=" color:#800000;">listWidget</span><span
style=" color:#000000;">-></span><span style=" color:#000000;">setSelectionMode</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QAbstractItemView</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">SingleSelection</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#800080;">Widget</span><span style=" color:#000000;">::~</span><span
style=" font-style:italic; color:#000000;">Widget</span><span style=" color:#000000;">()</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">delete</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#800000;">ui</span><span style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
</div>
头文件增加了上一节用到过的文件对话框，文件类、文本流等，<QListWidgetItem>
是用于从列表控件的行里提取文本用的，<QDataStream> 是本节的串行化数据流。<br>
构造函数里只增加了一句代码，用于设置列表控件为每次只能选中一行，这样删除行时只需要删除一行，简化操作。<br>
<br>
接下来是四个按钮对应的槽函数代码，先看看 "添加行" 按钮对应的槽函数：<br>
<div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
</span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">on_pushButtonAdd_clicked</span><span style=" color:#000000;">()</span>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strName</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-></span><span
style=" color:#800000;">lineEditName</span><span style=" color:#000000;">-></span><span
style=" color:#000000;">text</span><span style=" color:#000000;">().</span><span
style=" color:#000000;">trimmed</span><span style=" color:#000000;">();</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strAge</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-></span><span
style=" color:#800000;">lineEditAge</span><span style=" color:#000000;">-></span><span
style=" color:#000000;">text</span><span style=" color:#000000;">().</span><span
style=" color:#000000;">trimmed</span><span style=" color:#000000;">();</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strWeight</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-></span><span
style=" color:#800000;">lineEditWeight</span><span style=" color:#000000;">-></span><span
style=" color:#000000;">text</span><span style=" color:#000000;">().</span><span
style=" color:#000000;">trimmed</span><span style=" color:#000000;">();</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//判断三个数据项是否为空</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strName</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">||</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strAge</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">||</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strWeight</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"添加行"</span><span style=" color:#000000;">),</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"请填好姓名、年龄、体重三个数据项再添加。"</span><span style=" color:#000000;">));</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//计算出年龄和体重</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">qint32</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nAge</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strAge</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">toInt</span><span
style=" color:#000000;">();</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">double</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblWeight</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">strWeight</span><span style=" color:#000000;">.</span><span
style=" color:#000000;">toDouble</span><span style=" color:#000000;">();</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//判断范围</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">(</span><span
style=" color:#000000;">nAge</span><span style=" color:#000000;"><</span><span
style=" color:#000080;">0</span><span style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">||</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">(</span><span
style=" color:#000000;">nAge</span><span style=" color:#000000;">></span><span
style=" color:#000080;">600</span><span style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"添加行"</span><span style=" color:#000000;">),</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"年龄数值不对，应该</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">0~600</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">"</span><span style=" color:#000000;">));</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblWeight</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;"><</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">0.1</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"添加行"</span><span style=" color:#000000;">),</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"体重数值不对，至少</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">0.1kg</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">"</span><span style=" color:#000000;">));</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//对于正常数据，添加新行到列表控件</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strAll</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsLine</span><span
style=" color:#000000;">(&</span><span style=" color:#000000;">strAll</span><span
style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsLine</span><span
style=" color:#000000;"><<</span><span style=" color:#000000;">strName</span><span
style=" color:#000000;"><<</span><span style=" color:#008000;">"\t"</span><span
style=" color:#000000;"><<</span><span style=" color:#000000;">nAge</span><span
style=" color:#000000;"><<</span><span style=" color:#008000;">"\t"</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;"><<</span>fixed<span
style=" color:#000000;"><<</span><span style=" color:#000000;">qSetRealNumberPrecision</span><span
style=" color:#000000;">(</span><span style=" color:#000080;">2</span><span style=" color:#000000;">)<<</span><span
style=" color:#000000;">dblWeight</span><span style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-></span><span style=" color:#800000;">listWidget</span><span
style=" color:#000000;">-></span><span style=" color:#000000;">addItem</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strAll</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
</div>
这个槽函数先获取三个单行编辑器的文本，判断文本是否有空串，如果全部非空，再继续后面操作。<br>
对于三个非空字符串，根据年龄、体重的字符串转为数值 nAge、dblWeight ，然后对年龄、体重数值做一下简单判断。<br>
nAge、dblWeight 经过判断之后，我们定义字符串 strAll，用于保存三个数据项生成的文本，我们用文本流 tsLine
将三个数据项按照指定格式输出到 strAll 里面，最后把 strAll 添加到列表控件。<br>
<br>
"删除行" 按钮对应的槽函数代码就很简单了：<br>
<div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
</span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">on_pushButtonDel_clicked</span><span style=" color:#000000;">()</span>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//获取列表控件选中的行</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCurRow</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-></span><span
style=" color:#800000;">listWidget</span><span style=" color:#000000;">-></span><span
style=" color:#000000;">currentRow</span><span style=" color:#000000;">();</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//判断序号是否合法</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCurRow</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;"><</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">0</span><span style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//没有选中行</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//对于正常选中的行，删除掉</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800000;">ui</span><span
style=" color:#000000;">-></span><span style=" color:#800000;">listWidget</span><span
style=" color:#000000;">-></span><span style=" color:#000000;">takeItem</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCurRow</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
</div>
判断当前行号，然后删除列表控件里面的行即可。<br>
<br>
接着是 "保存DS" 按钮对应的槽函数，里面有写入 DS 文件格式代码：<br>
<div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
</span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">on_pushButtonSaveDS_clicked</span><span style=" color:#000000;">()</span>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//总行数</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">int</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCount</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-></span><span
style=" color:#800000;">listWidget</span><span style=" color:#000000;">-></span><span
style=" color:#000000;">count</span><span style=" color:#000000;">();</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//判断是否有数据</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">nCount</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;"><</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000080;">1</span><span style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//没数据，不用写</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//获取要保存的文件名</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strFileName</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">QFileDialog</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">getSaveFileName</span><span style=" color:#000000;">(</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">this</span><span
style=" color:#000000;">,</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"保存为</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">DS</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">文件"</span><span
style=" color:#000000;">),</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"."</span><span style=" color:#000000;">),</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"DS</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">files(*.ds);;All</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">files(*)"</span><span style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strFileName</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//没有保存文件名</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//有保存文件名，打开该文件供写入</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QFile</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">strFileName</span><span
style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">!</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">.</span><span style=" font-style:italic; color:#000000;">open</span><span
style=" color:#000000;">(</span><span style=" color:#800080;">QIODevice</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">WriteOnly</span><span
style=" color:#000000;">))</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"无法打开文件"</span><span style=" color:#000000;">),</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"无法打开要写入的文件："</span><span
style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">+</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">errorString</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//现在有输出文件对象，构造输出流</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QDataStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dsOut</span><span
style=" color:#000000;">(&</span><span style=" color:#000000;">fileOut</span><span
style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//设置流的版本</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dsOut</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">setVersion</span><span
style=" color:#000000;">(</span><span style=" color:#800080;">QDataStream</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">Qt_4_8</span><span
style=" color:#000000;">);</span></pre>
<pre style="-qt-paragraph-type:empty; margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><br></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//先写文件头，都用</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">qt</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">定义的整型变量输出</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dsOut</span><span
style=" color:#000000;"><<</span><span style=" color:#800080;">qint16</span><span
style=" color:#000000;">(</span><span style=" color:#000080;">0x4453</span><span
style=" color:#000000;">);</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//'D'</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">'S'</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dsOut</span><span
style=" color:#000000;"><<</span><span style=" color:#800080;">qint16</span><span
style=" color:#000000;">(</span><span style=" color:#000080;">0x0100</span><span
style=" color:#000000;">);</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//1.0版本文件格式</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dsOut</span><span
style=" color:#000000;"><<</span><span style=" color:#800080;">qint32</span><span
style=" color:#000000;">(</span><span style=" color:#000000;">nCount</span><span
style=" color:#000000;">);</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//行计数</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//每行的三个数据项</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strCurName</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">qint32</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCurAge</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">double</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dblCurWeight</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//从列表控件按行读取数据，然后写入到文件</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">for</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">int</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">i</span><span style=" color:#000000;">=</span><span style=" color:#000080;">0</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">i</span><span
style=" color:#000000;"><</span><span style=" color:#000000;">nCount</span><span
style=" color:#000000;">;</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">i</span><span
style=" color:#000000;">++)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strLine</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800000;">ui</span><span style=" color:#000000;">-></span><span
style=" color:#800000;">listWidget</span><span style=" color:#000000;">-></span><span
style=" color:#000000;">item</span><span style=" color:#000000;">(</span><span style=" color:#000000;">i</span><span
style=" color:#000000;">)-></span><span style=" color:#000000;">text</span><span
style=" color:#000000;">();</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QTextStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsLine</span><span
style=" color:#000000;">(&</span><span style=" color:#000000;">strLine</span><span
style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//从该行文本提取三个数据项</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tsLine</span><span
style=" color:#000000;">>></span><span style=" color:#000000;">strCurName</span><span
style=" color:#000000;">>></span><span style=" color:#000000;">nCurAge</span><span
style=" color:#000000;">>></span><span style=" color:#000000;">dblCurWeight</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//写入到文件</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dsOut</span><span
style=" color:#000000;"><<</span><span style=" color:#000000;">strCurName</span><span
style=" color:#000000;"><<</span><span style=" color:#000000;">nCurAge</span><span
style=" color:#000000;"><<</span><span style=" color:#000000;">dblCurWeight</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//提示写入完毕</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">information</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"保存DS文件"</span><span style=" color:#000000;">),</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"保存为</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">.ds</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">文件成功！"</span><span
style=" color:#000000;">));</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">}</span></pre>
</div>
这个槽函数先判断列表控件的数据行数，没数据就不处理。<br>
接着获取要保持的文件名，并判断文件名是否为空。<br>
有保存文件名之后，定义文件对象 fileOut，并以只写模式打开文件。<br>
打开文件成功之后构造串行化输出流 dsOut，设置流的版本号为 QDataStream::Qt_4_8。<br>
接下来是自定文件格式的写入，写入魔力数字 0x4453、版本号 0x0100 和 数据的行数 nCount。<br>
写入文件时，需要注意把整型数都转成 Qt 定义的 qint16、qint32 等类型，明确占用的比特位数。<br>
接着就是每个数据行的写入过程，使用 for 循环取出列表控件每行的文本 strLine ，<br>
然后根据文本 strLine 指针定义文本流 tsLine，从 tsLine 提取三个数据项
strCurName、nCurAge、dblCurWeight。<br>
得到三个数值变量之后，按顺序写入串行化输出流 dsOut 。<br>
注意我们这里说的一行数据只是个概念，没有真的写入换行符，因为二进制文件读写压根不用换行符，"行" 这个字仅仅是方便理解数据的排布而已。<br>
写完所有行的数据之后，弹出消息框，提示保存完毕。<br>
<br>
与保存文件函数相反的，就是 "加载DS" 按钮对应的槽函数：<br>
<div class="code"><span style=" color:#808000;">void</span><span style=" color:#c0c0c0;">
</span><span style=" color:#800080;">Widget</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">on_pushButtonLoadDS_clicked</span><span style=" color:#000000;">()</span>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//获取要打开的文件名</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QString</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strFileName</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#800080;">QFileDialog</span><span style=" color:#000000;">::</span><span
style=" color:#000000;">getOpenFileName</span><span style=" color:#000000;">(</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">this</span><span
style=" color:#000000;">,</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"打开DS文件"</span><span
style=" color:#000000;">),</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"."</span><span style=" color:#000000;">),</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"DS</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">files(*.ds);;All</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">files(*)"</span><span style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//判断文件名</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strFileName</span><span
style=" color:#000000;">.</span><span style=" color:#000000;">isEmpty</span><span
style=" color:#000000;">()</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//文件对象</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QFile</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileIn</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">strFileName</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//打开</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">!</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">fileIn</span><span
style=" color:#000000;">.</span><span style=" font-style:italic; color:#000000;">open</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QIODevice</span><span
style=" color:#000000;">::</span><span style=" color:#800080;">ReadOnly</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//打开失败</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"打开DS文件"</span><span style=" color:#000000;">),</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"打开DS文件失败:</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">"</span><span style=" color:#000000;">)</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">+</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">fileIn</span><span style=" color:#000000;">.</span><span
style=" color:#000000;">errorString</span><span style=" color:#000000;">());</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//构造输入数据流</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QDataStream</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dsIn</span><span style=" color:#000000;">(&</span><span
style=" color:#000000;">fileIn</span><span style=" color:#000000;">);</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//读取文件头</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">qint16</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nDS</span><span style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">qint16</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nVersion</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">qint32</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">nCount</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">dsIn</span><span
style=" color:#000000;">>></span><span style=" color:#000000;">nDS</span><span
style=" color:#000000;">>></span><span style=" color:#000000;">nVersion</span><span
style=" color:#000000;">>></span><span style=" color:#000000;">nCount</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//判断</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">nDS</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">数值</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000080;">0x4453</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">!=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">nDS</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"打开文件"</span><span style=" color:#000000;">),</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"指定的文件不是</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">.ds</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">文件类型，无法加载。"</span><span style=" color:#000000;">));</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">return</span><span
style=" color:#000000;">;</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">}</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">//判断版本号目前只有</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#008000;">1.0</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#808000;">if</span><span
style=" color:#000000;">(</span><span style=" color:#c0c0c0;"> </span><span style=" color:#000080;">0x0100</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">!=</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">nVersion</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#000000;">)</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">{</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#800080;">QMessageBox</span><span
style=" color:#000000;">::</span><span style=" color:#000000;">warning</span><span
style=" color:#000000;">(</span><span style=" color:#808000;">this</span><span style=" color:#000000;">,</span><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span style=" color:#000000;">(</span><span
style=" color:#008000;">"打开文件"</span><span style=" color:#000000;">),</span></pre>
<pre style=" margin-top:0px; margin-bottom:0px; margin-left:0px; margin-right:0px; -qt-block-indent:0; text-indent:0px;"><span
style=" color:#c0c0c0;"> </span><span style=" color:#000000;">tr</span><span
style=" color:#000000;">(</span><span style=" color:#008000;">"指定的</span><span style=" color:#c0c0c0;"> </span><span
style=" color:#008000;">.ds</span><span style=" color:#c0c0c0;"> </span><span style=" color:#008000;">文件格式版本不是</span><span